Benefits
Oral niacinamide studied in sun-damaged, high-risk skin
In a 12-month trial of 386 people who had already had at least two non-melanoma skin cancers, 500 mg twice daily was followed by 23% fewer new skin cancers and fewer actinic keratoses than placebo, and the difference disappeared after stopping. A similar trial in 158 organ-transplant recipients found no difference (rate ratio 1.0). This is a dermatology-patient finding, not a skin-appearance benefit for healthy users.
NAD+ precursor (vitamin B3 role)
Niacinamide is a form of vitamin B3 that the body uses to make NAD, a coenzyme needed by more than 400 enzymes in energy metabolism and DNA maintenance. In a 14-day trial in healthy adults, 500 mg a day of nicotinamide did not raise circulating NAD+, while nicotinamide riboside and NMN did, so a supplement dose may not raise blood NAD+ in well-fed people.
Skin response to UV light in healthy volunteers
In two 30-day studies in healthy adults taking 2,000 mg a day, the UVA dose needed to redden the skin rose by 26%, but UVB redness did not change, and neither study found less UV-induced DNA damage (thymidine dimers) in skin or urine. The UVB study was not randomized, and 2,000 mg a day is more than twice the EU upper limit for nicotinamide.
Mechanism of action
NAD+ precursor role
Niacinamide can be turned into NAD+ through the salvage pathway, and NAD is used by more than 400 enzymes, including those of energy metabolism. In a 14-day trial in healthy adults, however, 500 mg a day of nicotinamide did not raise blood NAD+, while nicotinamide riboside and NMN did, so how much extra NAD+ a supplement dose provides in well-fed people is uncertain.
Photoimmunoprotection (proposed mechanism for the skin-cancer trial)
In lab studies of human skin cells and skin samples, nicotinamide helped cells keep their energy supply after UV exposure and sped repair of UV-induced DNA damage, and it has been reported to reduce UV-induced immune suppression in skin. These are proposed explanations, not proven ones: in healthy volunteers taking 2,000 mg a day, UV-induced DNA damage markers in skin did not fall.
Clinical trials
Phase 3 randomized, double-blind, placebo-controlled trial: nicotinamide 500 mg twice daily or placebo for 12 months in people who had at least two non-melanoma skin cancers in the previous 5 years, followed for 18 months. (Chen et al. 2015, N Engl J Med)
386 adults with at least two non-melanoma skin cancers in the previous 5 years
The primary outcome, new non-melanoma skin cancers over 12 months, was 23% lower with nicotinamide (P=0.02). Basal-cell carcinomas were 20% lower (P=0.12, not significant) and squamous-cell carcinomas 30% lower (P=0.05). Actinic keratoses were 11% to 20% lower at each 3-month visit (13% at 12 months, P=0.001). Adverse events were similar to placebo, and there was no benefit after nicotinamide was stopped.
Phase 3 randomized, placebo-controlled trial: nicotinamide 500 mg or placebo twice daily for 12 months in organ-transplant recipients with at least two keratinocyte skin cancers in the past 5 years; stopped early for poor recruitment. (Allen et al. 2023, N Engl J Med)
158 immunosuppressed solid-organ transplant recipients
There were 207 new keratinocyte cancers with nicotinamide and 210 with placebo (rate ratio 1.0, P=0.96). Squamous-cell and basal-cell counts, actinic keratoses and quality of life did not differ, and adverse events were similar.
Randomized intraindividual trial: healthy volunteers (skin types I to III) took nicotinamide 2,000 mg a day or Polypodium leucotomos extract 480 mg a day for 30 days, with UVA exposure tests before and after. (Faisal et al. 2026, Photochem Photobiol Sci)
50 healthy adults with fair to light skin, randomized to nicotinamide or Polypodium
Nicotinamide raised the UVA dose needed to redden the skin by 26% (P=0.0008). UVA-induced thymidine dimers did not fall in skin (P=0.15) or urine (P=0.89).
Non-randomized intraindividual controlled trial: healthy volunteers (skin types I to III) took nicotinamide 2,000 mg a day or Polypodium leucotomos 480 mg a day for 30 days, with narrowband UVB tests before and after. (Faisal et al. 2025, Photochem Photobiol Sci)
47 healthy adults completed the study (nicotinamide and Polypodium groups combined)
Nicotinamide did not change the UVB dose needed to redden the skin (P=0.533) and did not significantly affect thymidine dimers in skin biopsies or urine.